1) Field of the Invention
The present invention relates to a feed screw device for driving a reciprocating mover, and particularly to a feed screw device suitable for use in, for example, a cleaning apparatus for a wire-type static eliminator or discharger employed in an electrostatic recording apparatus, and the like.
2) Description of the Related Art:
Heretofore, feed screws have been known in which spiral grooves or projections are formed on a shaft-shaped member by machining such as cutting and rolling to be used as threaded portions.
In addition, simple feed screws with no need for accuracy are also known wherein wire members are spirally wound on shaft-shaped members and fixed thereon over the entire length thereof.
In the above-described conventional feed screws, the threaded portions are constructed as rigid portions. Thus, the concept that the threaded portions be deformed is contradictory to common sense.
However, one example is known where a reciprocating mover to be carried by a feed screw is caused to collide with a stopper at the stroke ends of a driving action or the like so as to stop its movement. In this case, threaded portions of the feed screw and of a feed nut bite into one another due to impact force produced by the collision, or an excessive force is exerted on a reduction mechanism used for rotating and driving the feed screw. By way of example, when a simple worm gear system is employed in such a reduction mechanism, a worm shaft or the output shaft of a motor connected directly to the worm shaft is brought into a state in which an excessive thrust load is applied thereon, thus leading to difficulty in a subsequent reverse startup of the motor.